Technologies such as satellite navigation systems are useful for navigation and tracking movement of an object in an outdoor environment. However, these systems do not function well in areas without a clear pathway between the satellite and receiver, such as indoor, urban, subterranean and underwater environments, where satellite navigation system signals are often unavailable. Thus, it would be advantageous to have a positioning system that works in both outdoor and indoor environments that can be used in place of or in combination with a satellite navigation system.
Embodiments of the present invention determine performance information for an object based on local magnetic field data. The earth's magnetic field across a wide area is generally the same, with little variation. Thus, in most instances, a standard compass will generally point to the earth's magnetic pole. However, on a local level, the earth's magnetic field, although generally stable, may be non-uniform. Both the intensity and direction of the earth's magnetic field can vary locally. Of particular relevance, within a man-made structure such as a building, variations in the magnetic field can be influenced, for instance, by the building materials. For example, the magnetic field measured near a large steel support beam may be different than the magnetic field measured in the center of a large room. Accordingly, the intensity and direction of the magnetic field can vary when measured at various locations throughout a building.
By measuring and recording local magnetic field data, a magnetic field “map” of an area can be created that includes magnetic field information for the entire area. Measurements taken at a point later in time can be compared with the magnetic field map information to determine a location of an object within the mapped area. This can be useful for numerous activities, for example, navigating through a building or tracking the movement of an object within an enclosed structure. More specifically, certain athletic activities are commonly performed inside gyms, training facilities, arenas or stadiums that are partially or completely enclosed. For example, sports such as basketball, football and soccer are often played indoors. It is becoming increasingly important to track performance metrics of athletes during both training and competition. Satellite navigation system-based technology, although potentially useful in outdoor environments to track the position, movement and performance of players or sports equipment (e.g., a ball), often encounters accuracy problems in indoor environments. Thus, it would be advantageous to have a positioning system that is capable of tracking the position, movement and performance of players or sports equipment in indoor environments based on local magnetic field data.